Sen1, the yeast homolog of human senataxin, plays a more direct role than Rad26 in transcription coupled DNA repair

Abstract

Rad26, a DNA dependent ATPase that is homologous to human CSB, has been well known to play an important role in transcription coupled DNA repair (TCR) in the yeast Saccharomyces cerevisiae. Sen1, a DNA/RNA helicase that is essential for yeast cell viability and homologous to human senataxin, has been known to be required for transcriptional termination of short noncoding RNA genes and for a fail-safe transcriptional termination mechanism of protein-coding genes. Sen1 has also been shown to protect the yeast genome from transcription-associated recombination by resolving RNA:DNA hybrids naturally formed during transcription. Here, we show that the N-terminal non-essential region of Sen1 plays an important role in TCR, whereas the C-terminal nonessential region and the helicase activity of Sen1 are largely dispensable for the repair. Unlike Rad26, which becomes completely dispensable for TCR in cells lacking the TCR repressor Spt4, Sen1 is still required for efficient TCR in the absence of Spt4. Also unlike Rad26, which is important for repair at many but not all damaged sites in the transcribed strand of a gene, Sen1 is required for efficient repair at essentially all the damaged sites. Our results indicate that Sen1 plays a more direct role than Rad26 in TCR.

Single-nucleotide resolution dynamic repair maps of UV damage in Saccharomyces cerevisiae genome

“…Fig. 5B shows a screenshot of repair profiles of the SEN1 gene (6.7 kb), which codes for an important transcription-coupled repair protein Sen1 (34). Transcription-coupled repair of CPDs at the transcription start site (TSS) region of SEN1 peaks at 5 min, and then it decreases at 20 min and reaches its lowest level at the 1-h time point.…”

Transcription-coupled repair: an update

“…The Sen1 interactions with Rad2 and with the Rpb1 subunit of RNAPII suggested a role in TCR. Indeed, Sen1 deletions or mutations cause UV sensitivity, but the function of Sen1 in TCR has not been elucidated (Li et al 2016). To complicate things even further, a number of TCR suppressors have been found in yeast, including Spt4, Spt5, PAFc and the subcomplex Rpb4/Rpb7 (reviewed in Tatum and Li 2011).…”

Sen1 is required for RNA Polymerase III transcription termination in an R-loop independent manner

“…Importantly, the release and catch-up mechanism was also proposed to underlie the role of Mfd in both transcription-coupled repair and transcriptionreplication conflict resolution (Le et al, 2018). Strikingly, budding yeast Senataxin Sen1 has also been implicated in both transcription-coupled repair (Li et al, 2016) and transcription-replication conflict resolution (Alzu et al, 2012;Brambati et al, 2018;Mischo et al, 2011), strengthening the analogy with Mfd. A unifying way of interpreting the different roles of Senataxin Sen1 could therefore be to propose that it is targeted to chromatin through its interaction with RNA polymerases and that it subsequently patrols chromatin locally to facilitate the resolution of R-loops and/or stalled elongation complexes through a release and catch-up mechanism.…”

“…Concordant observations in human cells and budding yeast have established that Senataxin is important for transcription termination of at least a subset of RNAP2-transcribed genes (Porrua and Libri, 2013;Skourti-Stathaki et al, 2011;Steinmetz et al, 2006), although the mechanisms involved probably differ in both species as budding yeast Senataxin Sen1 contributes to RNAP2 transcription termination as part of the Nrd1-Nab3-Sen1 (NNS) complex, which is not conserved in human cells. In addition, Senataxin has been implicated in the repair of DNA damage (Andrews et al, 2018;Cohen et al, 2018;Li et al, 2016) and in the resolution of transcription-replication conflicts (Alzu et al, 2012;Richard et al, 2013;Yüce and West, 2013). Both budding and fission yeast homologues of Senataxin can translocate in a 5' to 3' direction on either single-stranded DNA or RNA in vitro (Han et al, 2017;Kim et al, 1999;Martin-Tumasz and Brow, 2015) and it is believed that long, co-transcriptional DNA:RNA hybrids (also known as R-loops) represent a critical substrate of Senataxin in vivo (reviewed in Groh et al, 2017).…”